A randomized, double-blinded, placebo-controlled study of pulse steroid therapy for patients at risk for developing bronchopulmonary dysplasia (BPD). Prove that: (1)Pulse steroid therapy will result in 30% decrease in infants of BPD; (2)There will be no difference in the incidence of side effects between two groups; (3)Pulse steroid therapy will not result in suppression of adrenal corticoid access; (4)Rate of somatic growth, measured by weight gain, length, and total body water will not vary between two groups.